The present invention relates to aluminum-zirconium antiperspirant salts made with zirconium salts having a low Zr:Cl ratio. The present invention also embraces methods of making these antiperspirant salts and compositions containing these antiperspirant salts.
Aluminum-zirconium antiperspirant salts have been known for several decades. See, for example, U.S. Pat. No. 2,814,585 (Daley), U.S. Pat. No. 2,854,382 (Grad), GB 1,353,916 (Bolich), U.S. Pat. No. 4,331,609 (Orr), U.S. Pat. No. 4,775,528 (Callaghan), U.S. Pat. No. 4,871,525 (Giovanniello), U.S. Pat. No. 4,900,534 (Inward), U.S. Pat. No. 5,225,187 (Carmody), U.S. Pat. No. 5,296,623 (Katsoulis), U.S. Pat. No. 5,330,751 (Curtin), EP 653,203 (Rosenberg), U.S. Pat. No. 5,718,876 (Parekh) and U.S. Pat. No. 5,955,064 (Giovanniello). Some of these aluminum-zirconium antiperspirant salts are described as having enhanced efficacy, which means that they provide greater sweat reduction than conventional antiperspirant salts. EP 653,203 (Rosenberg) suggests that such salts are improved by maintaining the molecular weight of the zirconium species as low as possible.
Prior to the discovery of the enhanced Alxe2x80x94Zr salts, U.S. Pat. No. 4,331,609 suggested that Alxe2x80x94Zr salts with a metal to chloride ratio below about 1.3 (e.g., 1.25) may be more efficacious than salts with a higher metal to chloride ratio. In U.S. Pat. No. 6,126,928 there are described certain polyhydric alcohol solutions of the salts described in the aforementioned ""609 patent. More recently, U.S. Pat. No. 6,375,937 described aluminum-zirconium tetrachlorohydrex glycine salts having a metal to chloride ratio in the range of 0.9 to 1.2 and a glycine to zirconium ratio greater than 1.3. None of these disclosures suggest that any advantage is obtained through the use of a particular zirconium species.
The present invention embraces enhanced efficacy aluminum-zirconium chlorohydrate antiperspirant salts having a metal (Al+Zr) to chloride ratio of about 0.9 to about 1.2, preferably about 0.9 to about 1.1, most preferably about 0.9 to about 1.0. To achieve the highest possible antiperspirant efficacy, these salts are made with or include a zirconium hydroxychloride of the formula Zr(OH)4xe2x88x92bClb wherein b is about 2.8 to about 4.0, preferably about 3.2 to about 4.0, so that the Zr:Cl ratio in said zirconium hydroxychloride is about 0.36 to about 0.25, preferably about 0.31 to about 0.25. The present invention also embraces methods of making such antiperspirant salts and aqueous solutions of such antiperspirant salts. The present invention further embraces topical compositions comprising a dermatologically acceptable carrier and a perspiration reducing effective amount of an aluminum-zirconium antiperspirant salt as described above.
The present invention embraces enhanced efficacy aluminum-zirconium chlorohydrate antiperspirant salts having a metal (Al+Zr) to chloride ratio of about 0.9 to about 1.2, preferably about 0.9 to about 1.1, most preferably about 0.9 to about 1.0. The Alxe2x80x94Zr salts generally have the empirical formula AlnZr(OH)[3n+4xe2x88x92m(n+1)](Cl)[m(n+1)] where n is 2.0 to 10.0, preferably 3.0 to 8.0, and m is about 0.83 to about 1.11 (which corresponds to M:Cl≅1.2-0.9), preferably about 0.90 to about 1.11 (which corresponds to M:Cl≅1.1-0.9), and more preferably about 1.00 to about 1.11 (which corresponds to M:Cl≅1.0-0.9). These salts also will typically include an amino acid such as glycine, alanine, valine, serine, leucine, or aminobutyric acid, preferably glycine, generally in an amount to provide an amino acid to zirconium ratio (e.g., Gly:Zr) of about 0.8 to about 4.0, preferably about 1.0 to about 2.0. These salts also generally have some water of hydration associated with them, typically on the order of 1 to 5 moles per mole of salt (typically, about 1% to about 16%, more typically about 4% to about 13% by weight). These salts are generally referred to as aluminum-zirconium tetrachlorohydrates when the Al:Zr ratio is between 2 and 6 and as aluminum-zirconium octachlorohydrates when the Al:Zr ratio is between 6 and 10.
A critical feature of the present invention is that the aluminum-zirconium chlorohydrate salts must be made with or include a zirconium hydroxychloride having a low Zr:Cl ratio. The Zr:Cl ratio preferably will be about 0.25 to about 0.36, more preferably about 0.25 to about 0.31, and most preferably about 0.25 to about 0.29. Preferred zirconium salts are those having the general formula Zr(OH)4xe2x88x92bClb wherein b is about 2.8 to about 4.0 (i.e., Zr:Cl ≅0.36-0.25), more preferably about 3.2 to about 4.0 (i.e., Zr:Cl≅0.31-0.25), most preferably about 3.4 to about 4.0 (Zr:Cl≅0.29-0.25). (It should be noted that when b is 4, the zirconium salt is essentially ZrCl4.) The zirconium salts, when used as a powder, generally have some water of hydration associated with them, typically on the order of 1 to 7 moles per mole of salt. In addition, the zirconium salts will usually include an amino acid, as described above, to prevent gellation in aqueous solution. Zirconium salts with a low Zr:Cl ratio are preferred because such salts appear to have a lower molecular weight than other zirconium salts and appear to maintain the lower molecular weight form even after being combined with the aluminum salt to form the aluminum-zirconium chlorohydrate. It is theorized that the presence of the low molecular weight zirconium species results in higher antiperspirant efficacy in the final Alxe2x80x94Zr salt. In addition, the use of zirconium salts with a low Zr:Cl ratio also facilitates the manufacture of the Alxe2x80x94Zr salt with a low metal:Cl ratio.
The Alxe2x80x94Zr salt compositions of the present invention are manufactured by mixing in an aqueous solution an aluminum antiperspirant salt (preferably an enhanced aluminum antiperspirant salt as described below) and a zirconium hydroxychloride salt (as described above), each salt being present in an amount to provide the desired Al:Zr molar ratio, and including in the aqueous solution sufficient chloride ion to provide the desired metal:chloride (M:Cl) ratio (i.e., about 0.9 to about 1.2, preferably about 0.9 to about 1.1, most preferably about 0.9 to about 1.0). If there is insufficient chloride ion provided by the aluminum and zirconium salts, additional chloride ion may be provided, for example, by addition of an appropriate amount of HCi (or other suitable chloride source such as AlCl3). Typically the mixing of components will take about 0.25 to 5 hours at room temperature (20-25xc2x0 C.). The aqueous solution of Alxe2x80x94Zr salt may be used or stored as an aqueous solution, or it may be spray dried or vacuum dried to obtain the salt in solid powder form. When the aluminum antiperspirant salt utilized is one with an elevated HPLC peak 4:3 area ratio, then preferably the Alxe2x80x94Zr salt will be dried to a solid while the peak 4:3 area ratio is above 0.4 to obtain a salt with maximum efficacy.
As an alternative to the above-described solution process, it is also possible to dry blend an aluminum antiperspirant salt with the zirconium hydroxychloride, provided that the molar quantities of Al, Zr, and Cl in the starting components that are blended are such as to provide the correct molar ratios of Al:Zr and M:Cl in the final product.
Preferred aluminum salts for use as starting materials are those having the general formula Al2(OH)6xe2x88x92aCla wherein a is about 0.3 to about 5, preferably about 0.8 to about 2.5, more preferably about 1 to about 2 (such that the Al to Cl mole ratio is about 0.9:1 to about 2.1:1). These salts generally have some water of hydration associated with them, typically on the order of 1 to 6 moles per mole of salt. Most preferably the aluminum salt is aluminum chlorohydrate, especially 5/6 basic aluminum chlorohydrate where a is about 1, such that the aluminum to chlorine mole ratio is about 1.9:1 to 2.1:1, typically about 1.95:1. Aluminum chlorohydrate is referred to as xe2x80x9cACHxe2x80x9d herein.
Preferably, the ACH is an enhanced efficacy form, sometimes written as ACHxe2x80x2, which has an HPLC peak 4 to peak 3 area ratio of at least 0.5, preferably at least 0.7, with at least 70%, preferably at least 80%, of the aluminum contained in peaks 3 and 4. The enhanced efficacy aluminum chlorohydrates are readily made by heating a dilute ACH solution (e.g., about 10% salt concentration by weight) at about 80-100xc2x0 C. for about 4 to 20 hours. It has been found that the greatest antiperspirant efficacy in the final Alxe2x80x94Zr antiperspirant salt can be obtained when an enhanced efficacy aluminum antiperspirant salt is used as one of the starting materials. As an alternative to or in conjunction with the above-described aluminum salt, it is also possible to employ aluminum chloride (AlCl3), provided that the molar ratio of the various reactants is adjusted to arrive at the desired molar ratio of the aluminum, zirconium, hydroxyl and chloride moieties in the final Alxe2x80x94Zr salt prepared.
The aluminum-zirconium chlorohydrate salts of the present invention generally have superior antiperspirant efficacy and, surprisingly, maintain the superior antiperspirant efficacy even when stored as an aqueous solution. This is a distinct advantage over previously known enhanced antiperspirant salts, whose efficacy deteriorates in aqueous solution.
The antiperspirant salts of the present invention may be formulated into topical compositions such as liquids (e.g., for roll-on or porous applicators), lotions, creams, gels, soft-solids, solid sticks, etc. Such compositions will comprise the antiperspirant salt in a perspiration reducing effective amount and a dermatologically acceptable carrier.
In particular, aqueous solutions of these antiperspirant salts may be directly utilized in oil-in-water and water-in-oil emulsions, such as the currently popular clear gel formulations, or in other aqueous based compositions such as aqueous based roll-ons. Preferred aqueous liquid compositions will comprise about 8% to about 45% (USP) by weight, preferably about 18% to about 38% (USP) by weight, antiperspirant salt and about 20% to about 90%, preferably about 45% to about 80%, water, such aqueous compositions optionally including other water soluble cosmetic ingredients (e.g., ethanol or polyhydric alcohol). These aqueous solutions may be stored indefinitely without significant loss of efficacy, unlike solutions of conventional enhanced efficacy salts, and may be diluted to an appropriate concentration (e.g., 6%-22% USP) for topical application when formulated into a commercial product.
It is also possible to make a solution of the Alxe2x80x94Zr antiperspirant salt in a liquid polyhydric alcohol such as propylene glycol. The liquid polyhydric alcohol will typically have from three to six carbon atoms and from two to six hydroxyl groups. Such a solution may be readily obtained by adding the polyhydric alcohol to an aqueous solution of the Alxe2x80x94Zr salt as described above, then evaporating off the water under vacuum (see, for example, U.S. Pat No. 5,643,558). Such a polyhydric alcohol composition may advantageously comprise about 8% to about 45% (USP) of said antiperspirant salt. This product can then be readily formulated into topical antiperspirant compositions which use a polyhydric alcohol vehicle, such as clear sticks gelled with dibenzylidene sorbitol or other gellants (see, for example, U.S. Pat. No. 5,705,171).
It is especially preferred to produce the Alxe2x80x94Zr salts of the present invention in solid powder form, for example by spray drying or vacuum drying the aqueous solution in which these salts are produced. The powdered antiperspirant salts may then be formulated into any known type of topical composition which utilizes powdered salts, including, in particular, liquid roll-on, cream, soft-solid and solid stick formulations in which the powdered salt is suspended in an anhydrous, dermatologically acceptable carrier, particularly a carrier comprising a silicone (e.g., cyclomethicone, dimethicone, etc.), typically at a concentration of about 6% to about 22% (USP) active by weight.
The present invention also embraces a method of inhibiting or reducing perspiration by topically applying an effective amount of an antiperspirant composition as described herein to the skin of a human, preferably to the axilla, where such reduction in perspiration is desired by the user. An effective amount is that amount which provides at least a 20% sweat reduction, preferably at least a 40% sweat reduction, when tested in accordance with a standard hot room thermal efficacy protocol, and most preferably that amount which reduces perspiration to a degree that is noticeable by the user. Typically, the amount of antiperspirant composition applied will range from about 0.1 gram to about 1.0 gram per axilla depending on the formulation or such amount as will deliver about 0.01 to about 0.25 gram of antiperspirant active per axilla.
The present invention may be further illustrated by the following examples in which the parts and percentages are by weight. In these examples, the abbreviation ACHxe2x80x2 means enhanced efficacy 5/6 basic aluminum chlorohydrate with an Al:Cl ratio of about 1.95 and having an HPLC peak 4 to peak 3 area ratio of at least 0.7 with at least 80% of the aluminum contained in peaks 3 and 4. The ACHxe2x80x2 is made by diluting ACH with water to form a solution of about 10% concentration, heating the dilute ACH solution at about 85xc2x0 C. for about 16 hours, then rapidly concentrating the ACHxe2x80x2 by vacuum evaporation (for example, using a falling film evaporator) to a concentration of about 42% USP active and cooling to room temperature. The ACHxe2x80x2 must be used shortly after preparation in order to insure that it has the desired high peak 4 to peak 3 ratio.
The abbreviation ZHCG means zirconium hydroxychloride-glycine (Zr:Gly≅1). When referring to this material, the Zr:Cl ratio (e.g., Zr:Cl=0.28) will be indicated in parentheses following the abbreviation. The ZHCG may be prepared by reacting zirconium basic carbonate with an appropriate amount of HCl to achieve the desired Zr:Cl ratio, then adding the appropriate amount of glycine. The aqueous ZHCG used in the examples has a Zr content of about 8% by weight Zr. The abbreviation AZCH means aluminum-zirconium chlorohydrate-gly (standard efficacy), EAZCH means a conventional enhanced efficacy AZCH with high peak 4:3 ratio, and Exe2x80x3AZCH means an enhanced efficacy AZCH of the present invention with a low M:Cl ratio and made with a ZHCG having a low Zr:Cl ratio. xe2x80x9cComp.xe2x80x9d means comparative example.